An IP Multimedia Core Network Subsystem (referred to as IMS) is an IP-based network architecture proposed by the 3rd Generation Partnership Project (referred to as 3GPP), and it constructs an open and flexible service environment to support multimedia applications and provide the users with enriched multimedia services.
The 3GPP standard organization studies on the Enhanced Single Radio Voice Call Continuity (referred to as eSRVCC), and publishes multiple standards, for example, an eSRVCC network element networking frame is stipulated in the standards such as the 3GPP TS 23.237 and the 3GPP TS 24.237. FIG. 1 shows a schematic diagram of an eSRVCC network element networking frame in related art. As shown in FIG. 1, in the eSRVCC technology, the function of an Access Transfer Control Function (referred to as ATCF) is very important. Several important parameters involved in the ATCF in this figure and the functions thereof are described as follows:
A Session Transfer Number-Single Radio (referred to as STN-SR) is allocated by the ATCF and is used for identifying an ATCF network element. A Mobile Switch Centre Server (referred to as MSC server) sends a switch request to a correct ATCF according to the STN-SR.
An Access Transfer Update-Session Transfer Identifier (referred to as ATU-STI) is allocated by a Service Continuity and Centralization Application Server (referred to as SCC AS) and is notified to the ATCF, used for filling an Uniform Resource Identifier (referred to as URI) of an invite message (also called request URI) in a request that the ATCF initiates call switch to the SCC AS.
A Correlation-Mobile Subscriber International Intergrated Service Digital Network (ISDN) Number (referred to as C-MSISDN) is acquired by the SCC AS from a Home Subscriber Server (referred to as HSS) and is notified to the ATCF, used for achieving the correlation of a Packet Switch (referred to as PS) call and a Circuit Switch (referred to as CS) call in the call switch.
The above-mentioned parameters are all allocated and acquired after a User Equipment (referred to as UE) is registered. If the UE does not initiate the registration, there is no such information about the UE on the ATCF and the SCC AS. The processing technology in the related art of the above-mentioned parameter information about the UE is described below.
The UE having the eSRVCC capability initiates the registration to an IMS domain. After a registration message arrives at the ATCF, the ATCF allocates the STN-SR to be filled in the ‘Feature-Caps’ header of the registration message and sends to an Interrogating Call Session Control Function (referred to as I-CSCF). After the UE is registered successfully on the CSCF, a host name or address of a Serving Call Session Control Function (referred to as S-CSCF) for serving the subscriber is returned and the ATCF stores the relevant data which is registered and returned. Meanwhile, the CSCF sends the STN-SR to the SCC AS via a third party registration flow. The SCC AS initiates a process of updating the STN-SR to the HSS, and notifies the ATCF of the C-MSISDN acquired from the HSS and the allocated ATU-STI via the Message message. The ATCF stores these data. After the UE is successfully registered, the ATCF provides the services of in-call, out-call, call/media anchoring and switch from a PS domain to a CS domain for the UE.
FIG. 2 shows a schematic diagram of a typical eSRVCC disaster recovery networking manner according to an embodiment of the disclosure. As shown in FIG. 2, the ATCF network element networks by means of disaster recovery and there is at least one pair of ATCF network elements. FIG. 3 shows a schematic diagram of an eSRVCC network element networking after the disaster recovery of a master ATCF according to an embodiment of the disclosure. As shown in FIG. 3, an ATCF1 (a master ATCF) has a breakdown, and the adjacent network elements have detected that the link between the network elements is interrupted. Thus, the UE needs to re-initiate the registration to a slave ATCF. After acquiring the above-mentioned relevant data which is registered and returned, the slave ATCF network element taken over by the disaster recovery provides for the normal call and switch services. However, when the UE re-registers, it needs to spend a certain period of time. During this period of time, the UE cannot carry out the normal services, thereby influencing user experience.
Therefore, there is a problem in the related art that how to recover a service as soon as possible when there is a breakdown on the master ATCF.